An image processing method and apparatus includes a color space conversion unit arranged to convert pixel data scanned by a line sensor of each color component into first chromaticity data and second chromaticity data, and an achromatic color determining unit arranged to determine whether or not the pixel data is achromatic. The achromatic color determining unit includes a comparison unit arranged to compare an achromatic color determination area with the pixel data in a color space defined by orthogonal coordinates having each chromaticity data as a coordinate axis. The achromatic color determination area is an elongated area that includes a coordinate origin of the color space, that is set based on a coordinate position of a false color acquired by using a size and position of displacement of the scanning position of each color component generated in accordance with the scanning speed, and that extends in an opposite direction from the coordinate origin.